1. Field of the Invention
Embodiments of the present invention relate in general to a semiconductor chip test apparatus for measuring a standby current being applied to a semiconductor chip from a power supply unit and a testing method for measuring the standby current.
2. Description of Related Art
Generally, a semiconductor integrated circuit undergoes an electrical characteristic test during fabrication to check whether it is normal or defective. For such an electrical characteristic test, a tester for generating an electrical signal and applying it to a semiconductor chip to be tested, and its peripheral auxiliary devices are used.
FIG. 1 illustrates an apparatus which enables a typical semiconductor chip tester to measure current by utilizing a common ground of the tester.
As shown in FIG. 1, the typical semiconductor chip test apparatus tests a semiconductor chip 10. The typical semiconductor chip test apparatus includes first and second power supply units 20 and 22, and a tester 30.
The semiconductor chip 10, which is a package to be tested, has a power input terminal VDD. It is also connected to a common ground VSS.
Each of the first and the second power supply units 20 and 22 serves to supply power to the power input terminal VDD of the semiconductor chip 10.
The tester 30 measures an output current (e.g., a standby current IDDS) of each of the first and the second power supply units 20 and 22.
In general, a semiconductor chip does not commonly use a ground, but each power supply unit has a separate ground. However, since most of semiconductor chip testers make use of a common ground as in FIG. 1, it is impossible to measure current flowing through different current paths, such as current paths flowing to an input/output (I/O) ground and to a core ground.
Therefore, a hot spot may not be detected upon analyzing defects, making a defect analysis on a current path difficult. During actual analysis of defects, current can frequently flow from the core side's power supply unit to the I/O ground or to the core ground.
In addition, many recently developed semiconductor chips are mobile product family chips, and thus a supply current or a standby current IDDS is a very critical parameter in testing such semiconductor devices. In system-on-chip (SOC) semiconductor chips there are several power supply units within the chip, each of which has a different ground, e.g., a PLL (Phase Locked Loop) ground, two core grounds, an I/O ground, etc.